KR20220169407A - Method and apparatus for transmitting and receiving frame considering length of data in communication system supporting multi-link - Google Patents

Abstract

Disclosed are a method and device for transmitting and receiving a frame in consideration of the length of data in a communication system supporting multiple links. A method of a first device comprises the steps of: receiving a first frame from a second device in a first TXOP on a first link; receiving a second frame from the second device in a second TXOP on a second link; performing a first backoff operation for transmitting a first reception response frame for the first frame on the first link; and transmitting "when the first backoff operation is completed and the reception of the second frame is completed", the first reception response frame to the second device on the first link. According to the present invention communication between devices (e.g., stations, access points) may be performed by using multiple links.

Description

Method and apparatus for transmitting and receiving frames considering the length of data in a communication system supporting multiple links

The present invention relates to a wireless local area network (WLAN) communication technology, and more particularly, to a technology for transmitting and receiving a response frame in a device that does not support a simultaneous transmit and receive (STR) operation.

Recently, as the spread of mobile devices expands, a wireless local area network (WLAN) technology capable of providing fast wireless communication services to mobile devices is receiving much attention. The wireless LAN technology may be a technology that allows mobile devices such as smart phones, smart pads, laptop computers, portable multimedia players, and embedded devices to wirelessly access the Internet based on wireless communication technology in a short distance.

As applications requiring higher throughput and applications requiring real-time transmission occur, the IEEE 802.11be standard, which is an Extreme High Throughput (EHT) wireless LAN technology, is being developed. A goal of the IEEE 802.11be standard may be to support throughput rates as high as 30 Gbps. The IEEE 802.11be standard may support a technique for reducing transmission delay. In addition, the IEEE 802.11be standard includes a more expanded frequency bandwidth (eg, 320 MHz bandwidth), multi-link transmission and aggregation operation including operation using multi-band, A multiple access point (AP) transmission operation and/or an efficient retransmission operation (eg, a hybrid automatic repeat request (HARQ) operation) may be supported.

However, since the multi-link operation is not defined in the existing WLAN standards, it may be necessary to define detailed operations according to the environment in which the multi-link operation is performed. In particular, when two or more links are adjacent, a simultaneous transmit and receive (STR) operation may not be performed in multiple links due to interference from adjacent links (eg, adjacent bands or adjacent channels). When the signal interference level between adjacent links is higher than a specific level, a channel sensing operation for transmission and/or a signal reception operation for transmission in another link may not be performed while a transmission operation is performed in one link due to the corresponding interference. In the above situation, a method for transmitting and receiving a frame based on a channel access procedure considering a transmission/reception state in one link may be required.

On the other hand, the background technology of the invention is prepared to enhance understanding of the background of the invention, and may include content other than the prior art already known to those skilled in the art to which the technology belongs.

An object of the present invention to solve the above problems is to provide a method and apparatus for transmitting and receiving a frame considering the length of data in a device that does not support a simultaneous transmit and receive (STR) operation in a communication system supporting multiple links. is to do

A method of a first device according to a first embodiment of the present invention for achieving the above object includes receiving a first frame from a second device in a first TXOP of a first link, in a second TXOP of a second link Receiving a second frame from the second device, performing a first backoff operation for transmission of a first reception response frame for the first frame in the first link, and "the first backoff operation" and transmitting the first reception response frame to the second device in the first link, when the operation is completed and reception of the second frame is completed, wherein the first TXOP is greater than the second TXOP Short, and the time point at which the reception of the second frame is completed is after the time point at which the reception of the first frame is completed.

An ACK policy field included in the MAC header of the first frame may be set to a value indicating NSTR ML ACK, and the ACK policy field set to a value indicating NSTR ML ACK may transmit the first reception response frame to the Transmission after completion of reception of the second frame may be instructed.

The first frame may include a BAR indicating NSTR ML ACK, and the BAR may indicate transmission of the first reception response frame after completion of reception of the second frame.

The first backoff operation may be performed using an EDCA parameter for AC of the first frame.

The first back-off operation is repeatedly performed until reception of the second frame is completed, or when the first back-off operation is completed before reception of the second frame is completed, the back-off operation for the first back-off operation is completed. The counter value may be maintained at 0 until reception of the second frame is completed, or the first backoff operation may be performed after reception of the second frame is completed.

When the first device is the AP MLD, the second device may be an STA MLD, and when the first device is the STA MLD, the second device may be the AP MLD, and the AP MLD may be the STA MLD. The STR operation may be supported in link 1 and the second link, and the STA MLD may not support the STR operation in the first link and the second link.

The STA1 associated with the STA MLD may perform a low-power operation in the first link from the end of the first frame to the end of the second frame.

A method of a first device according to a second embodiment of the present invention for achieving the above object includes receiving a first frame from a second device in a first TXOP of a first link, in a second TXOP of a second link Receiving a second frame from the second device, and when information included in the first frame indicates to transmit a first reception response to the first link through the second link, the first Transmitting the first reception response for the frame and the second reception response for the second frame to the second device on the second link, wherein the first TXOP is shorter than the second TXOP, wherein the The completion time of reception of the second frame is after the completion time of reception of the first frame.

The information may be an ACK policy field included in the MAC header of the first frame, and the ACK policy field may be set to a value indicating NSTR ML ACK.

The information may be a BAR included in the first frame.

The transmitting to the second device may include generating one reception response frame including the first reception response and the second reception response, and transmitting the one reception response frame to the second device. can include

The transmitting to the second device may include transmitting a first reception response frame including the first reception response to the second device, and transmitting a second reception response frame including the second reception response to the second device. 2 may include transmitting to the device.

When the first device is the AP MLD, the second device may be an STA MLD, and when the first device is the STA MLD, the second device may be the AP MLD, and the AP MLD may be the STA MLD. The STR operation may be supported in link 1 and the second link, and the STA MLD may not support the STR operation in the first link and the second link.

A method of a first device according to a third embodiment of the present invention for achieving the above object includes receiving a first frame from a second device in a first TXOP of a first link, in a second TXOP of a second link Receiving a second frame from the second device, and the information included in the first frame transmits a first reception response frame to the first frame to a third link that is not in a relationship between the first link and an NSTR link pair. and transmitting the first reception response frame to the second device through the third link when requesting transmission from .

The first link and the second link may be the NSTR link pair, the first TXOP may be shorter than the second TXOP, and the reception completion time of the second frame is after the reception completion time of the first frame can

The transmitting to the second device may include selecting the third link that does not have a relationship between the first link and the NSTR link pair among links mapped to the AC of the first frame; Performing a first backoff operation for transmission of a first reception response frame, and transmitting the first reception response frame to the second device through the third link when the first backoff operation is completed. can include

The third link may be selected based on TID-to-link mapping.

The first backoff operation in the third link may be performed using EDCA parameters for the AC of the first frame.

The information may be an ACK policy field included in the MAC header of the first frame, and the ACK policy field may be set to a value indicating NSTR ML ACK.

When the first device is the AP MLD, the second device may be an STA MLD, and when the first device is the STA MLD, the second device may be the AP MLD, and the AP MLD may be the STA MLD. The STR operation may be supported in link 1 and the second link, and the STA MLD may not support the STR operation in the first link and the second link.

According to the present application, communication between devices (eg, stations and access points) may be performed using multi-links. When some links (eg, some channels) among multiple links are adjacent to each other, a simultaneous transmit and receive (STR) operation may not be performed. When the lengths of the data units to be transmitted in the first link and the lengths of the data units to be transmitted in the second link are different, the device may equalize the lengths of the data units to be transmitted in the first link and the second link, and then set the lengths of the data units to be transmitted in the first link. and a simultaneous transmission operation in the second link. Therefore, transmission efficiency in the communication system can be improved.

1 is a block diagram showing a first embodiment of a communication node constituting a wireless LAN system.
2 is a conceptual diagram illustrating a first embodiment of multiple links established between MLDs.
3 is a timing diagram illustrating a first embodiment of a method of transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.
4 is a timing diagram illustrating a second embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.
5 is a timing diagram illustrating a third embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.
6 is a timing diagram illustrating a fourth embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.
7 is a timing diagram illustrating a fifth embodiment of a method of transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.
8 is a timing diagram illustrating a sixth embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a wireless LAN system supporting multiple links.
9A is a timing diagram illustrating a first embodiment of a MU transmission method in a WLAN system supporting multiple links.
9B is a timing diagram illustrating a second embodiment of a MU transmission method in a WLAN system supporting multiple links.
10 is a timing diagram illustrating a third embodiment of an MU transmission method in a WLAN system supporting multiple links.
11 is a timing diagram illustrating a fourth embodiment of a MU transmission method in a WLAN system supporting multiple links.
12 is a timing diagram illustrating a fifth embodiment of an MU transmission method in a WLAN system supporting multiple links.
13 is a timing diagram illustrating a sixth embodiment of a MU transmission method in a WLAN system supporting multiple links.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The term "and/or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

In embodiments of the present application, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B”. Also, in the embodiments of the present application, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B”.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

In the following, a wireless communication system to which embodiments according to the present invention are applied will be described. A wireless communication system to which embodiments according to the present invention are applied is not limited to the content described below, and embodiments according to the present invention can be applied to various wireless communication systems. A wireless communication system may be referred to as a “wireless communication network”.

In an embodiment, “setting an operation (eg, transmission operation)” means “setting information for the corresponding operation (eg, information element, parameter)” and/or “performing the corresponding operation”. It may mean that the "instructing information" is signaled. "Setting an information element (eg, parameter)" may mean that a corresponding information element is signaled. "Configuring a resource (eg, a resource region)" may mean that configuration information of a corresponding resource is signaled.

1 is a block diagram showing a first embodiment of a communication node constituting a wireless LAN system.

Referring to FIG. 1 , a communication node 100 may be an access point, a station, an access point (AP) multi-link device (MLD), or a non-AP MLD. An access point may mean an AP, and a station may mean an STA or a non-AP STA. An operating channel width supported by the access point may be 20 MHz (megahertz), 80 MHz, 160 MHz, or the like. The operating channel width supported by the station may be 20 MHz, 80 MHz, etc.

The communication node 100 may include at least one processor 110, a memory 120, and at least one transceiver 130 connected to a network to perform communication. The transceiver 130 may be referred to as a transceiver, a radio frequency (RF) unit, or an RF module. In addition, the communication node 100 may further include an input interface device 140, an output interface device 150, a storage device 160, and the like. Each component included in the communication node 100 may be connected by a bus 170 to communicate with each other.

However, each component included in the communication node 100 may be connected through an individual interface or an individual bus centered on the processor 110 instead of the common bus 170 . For example, the processor 110 may be connected to at least one of the memory 120, the transceiver 130, the input interface device 140, the output interface device 150, and the storage device 160 through a dedicated interface. .

The processor 110 may execute a program command stored in at least one of the memory 120 and the storage device 160 . The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 120 and the storage device 160 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 120 may include at least one of a read only memory (ROM) and a random access memory (RAM).

2 is a conceptual diagram illustrating a first embodiment of multi-link established between multi-link devices (MLDs).

Referring to FIG. 2, an MLD may have one medium access control (MAC) address. In embodiments, MLD may refer to AP MLD and/or non-AP MLD. The MAC address of the MLD may be used in a multi-link setup procedure between a non-AP MLD and an AP MLD. The AP MLD's MAC address may be different from the non-AP MLD's MAC address. Access point(s) associated with the AP MLD may have different MAC addresses, and station(s) associated with the non-AP MLD may have different MAC addresses. Access points in the AP MLD having different MAC addresses may be in charge of each link and may act as independent access points (APs).

Stations in the non-AP MLD having different MAC addresses may be in charge of each link and may act as independent stations (STAs). Non-AP MLD may be referred to as STA MLD. The MLD may support a simultaneous transmit and receive (STR) operation. In this case, the MLD can perform a transmit operation on link 1 and a receive operation on link 2. MLD supporting STR operation may be referred to as STR MLD (eg, STR AP MLD, STR non-AP MLD). In embodiments, a link may mean a channel or a band. A device that does not support the STR operation may be referred to as NSTR (non-STR) AP MLD or NSTR non-AP MLD (or NSTR STA MLD).

MLD can transmit and receive frames in multiple links by using a non-contiguous bandwidth extension method (eg, 80 MHz + 80 MHz). Multi-link operation may include multi-band transmission. An AP MLD may include a plurality of access points, and the plurality of access points may operate on different links. Each of the plurality of access points may perform function(s) of a lower MAC layer. Each of the plurality of access points may be referred to as a "communication node" or a "sub-entity". A communication node (ie, an access point) may operate under the control of an upper layer (or the processor 110 shown in FIG. 1). A non-AP MLD may include a plurality of stations, and the plurality of stations may operate on different links. Each of the plurality of stations may be referred to as a "communication node" or a "sub-entity". A communication node (ie, a station) may operate under the control of an upper layer (or the processor 110 shown in FIG. 1).

MLD can perform communication in multi-band. For example, MLD may perform communication using a 40 MHz bandwidth according to a channel extension method (eg, bandwidth extension method) in a 2.4 GHz band, and communicate using a 160 MHz bandwidth according to a channel extension method in a 5 GHz band. can be performed. The MLD may perform communication using a 160 MHz bandwidth in a 5 GHz band and may perform communication using a 160 MHz bandwidth in a 6 GHz band. One frequency band (eg, one channel) used by the MLD may be defined as one link. Alternatively, a plurality of links may be established in one frequency band used by the MLD. For example, the MLD can establish one link in the 2.4 GHz band and two links in the 6 GHz band. Each link may be referred to as a first link, a second link, a third link, and the like. Alternatively, each link may be referred to as link 1, link 2, link 3, and the like. A link number may be set by an access point, and an ID (identifier) may be assigned to each link.

An MLD (eg, an AP MLD and/or a non-AP MLD) may establish multiple links by performing an access procedure and/or a negotiation procedure for multi-link operation. In this case, the number of links and/or links to be used among multiple links may be set. A non-AP MLD (eg, a station) may check information on a band capable of communicating with the AP MLD. In a negotiation procedure for multi-link operation between the non-AP MLD and the AP MLD, the non-AP MLD may configure one or more links among links supported by the AP MLD to be used for the multi-link operation. A station that does not support multi-link operation (eg, an IEEE 802.11a/b/g/n/ac/ax station) may be connected to one or more links among multiple links supported by the AP MLD.

When a band interval between multiple links (eg, a band interval between link 1 and link 2 in the frequency domain) is sufficient, the MLD may perform the STR operation. For example, the MLD may transmit PPDU (physical) layer protocol data unit (PPDU) 1 using link 1 of multiple links, and may receive PPDU 2 using link 2 of multiple links. On the other hand, if the MLD performs the STR operation when the band interval between multiple links is not sufficient, in-device coexistence (IDC) interference, which is interference between multiple links, may occur. Therefore, if the bandwidth interval between multiple links is not sufficient, the MLD may not be able to perform the STR operation. A link pair having the aforementioned interference relationship may be a Non Simultaneous Transmit and Receive (NSTR) limited link pair. Here, the MLD may be NSTR AP MLD or NSTR non-AP MLD.

For example, multiple links including link 1, link 2, and link 3 may be established between the AP MLD and the non-AP MLD 1. If the bandwidth interval between links 1 and 3 is sufficient, the AP MLD may perform STR operation using links 1 and 3. That is, the AP MLD can transmit frames using link 1 and receive frames using link 3. If the bandwidth interval between links 1 and 2 is not sufficient, the AP MLD may not be able to perform STR operation using links 1 and 2. If the bandwidth interval between links 2 and 3 is not sufficient, the AP MLD may not be able to perform STR operation using links 2 and 3.

Meanwhile, a negotiation procedure for multi-link operation may be performed in an access procedure between a station and an access point in a wireless LAN system.

A device (eg, access point, station) supporting multiple links may be referred to as a multi-link device (MLD). An access point supporting multiple links may be referred to as an AP MLD, and a station supporting multiple links may be referred to as a non-AP MLD or STA MLD. The AP MLD may have a physical address (eg MAC address) for each link. The AP MLD may be implemented as if an AP in charge of each link exists separately. A plurality of APs can be managed within one AP MLD. Accordingly, coordination between a plurality of APs belonging to the same AP MLD may be possible. The STA MLD may have a physical address (eg, MAC address) for each link. The STA MLD may be implemented as if an STA in charge of each link exists separately. A plurality of STAs may be managed within one STA MLD. Accordingly, coordination between a plurality of STAs belonging to the same STA MLD may be possible.

For example, each of AP1 of the AP MLD and STA1 of the STA MLD may be in charge of a first link and may perform communication using the first link. Each of AP2 of the AP MLD and STA2 of the STA MLD may be in charge of the second link and may communicate using the second link. STA2 may receive state change information for the first link from the second link. In this case, the STA MLD may collect information (eg, state change information) received from each link, and may control an operation performed by STA1 based on the collected information.

Next, methods for transmitting and receiving data in a wireless LAN system will be described. Even when a method (for example, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is described as a method performed in the first communication node and a method (eg, signal transmission or reception) For example, receiving or transmitting a signal) may be performed. That is, when the operation of the STA is described, the corresponding AP may perform an operation corresponding to the operation of the STA. Conversely, when the operation of the AP is described, the corresponding STA may perform an operation corresponding to the operation of the AP. In an embodiment, the operation of the STA may be interpreted as the operation of the STA MLD, the operation of the STA MLD may be interpreted as the operation of the STA, the operation of the AP may be interpreted as the operation of the AP MLD, and the operation of the AP MLD can be interpreted as an operation of the AP.

FIG. 3 is a timing diagram illustrating a first embodiment of a method of transmitting and receiving frames when transmit opportunity (TXOP) limits are different from each other in a wireless LAN system supporting multiple links.

Referring to FIG. 3, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA MLD1 may operate as an NSTR STA MLD in a specific link pair (eg, a pair of first and second links), and may operate as an NSTR STA MLD in another link pair (eg, a pair of first and third links and/or Alternatively, a pair of the second link and the third link) may operate as an STR STA MLD. That is, the STA MLD1 cannot perform the STR operation on the first link and the second link pair, and can perform the STR operation on the first link and the third link pair and/or the second link and the third link pair. can

AP MLD1 can transmit and receive data frames with STA MLD1 using multiple links. AP1 of AP MLD1 and STA1 of STA MLD1 may operate on a first link, AP2 of AP MLD1 and STA2 of STA MLD1 may operate on a second link, and AP3 of AP MLD1 and STA3 of STA MLD1 may operate on a third link. Links can work. Each of AP1 and STA1 may perform a backoff operation for frame transmission in a first link, each of AP2 and STA2 may perform a backoff operation for frame transmission in a second link, and each of AP3 and STA3 may perform a backoff operation for frame transmission in a second link. In link 3, a backoff operation for frame transmission can be performed.

The backoff operation may be performed independently on each of the links. The backoff operation may be an Enhanced Distributed Channel Access Function (EDCAF). A backoff operation in links may be a backoff operation for the same Access Category (AC). Alternatively, the backoff operation in the links may be a backoff operation for different ACs. Multiple backoff operations (eg, multiple backoff operations for multiple ACs) may be performed in one link. Value(s) of Enhanced Distributed Channel Access (EDCA) parameter(s) for backoff operation may be different for each AC. The priority of AC may be defined as shown in Table 1 below, and the contention window (CW) of AC may be defined as shown in Table 2 below.

The backoff operation for synchronous transmission may be performed for the same AC in both the first link and the second link, and may use the same EDCA parameter(s). Counter values for backoff operations in the first link and the second link may be independently selected. The counter value may mean a backoff counter value. In one of the first link and the second link (eg, the first link), the backoff operation may succeed first when the backoff counter value becomes 0. For example, in a link (eg, a first link) for which a small backoff counter value is selected, the backoff operation may succeed first. In the first link where the backoff operation succeeds, the backoff counter value may be maintained at 0 until the backoff operation succeeds in another link (eg, the second link). In this case, transmission in the first link may be delayed (ie, standby).

STA1 of STA MLD1 simultaneously performs a backoff operation for AC_VI (hereinafter referred to as "AC_VI backoff operation") and a backoff operation for AC_VO (hereinafter referred to as "AC_VO backoff operation") in the first link. can The AC_VI backoff operation may succeed before the AC_VO backoff operation, and the AC_VI backoff counter value in the first link may be maintained at 0 until the backoff counter value in the second link becomes 0. The AC_VO backoff operation may be completed while waiting for transmission of AC_VI data in the first link. In this case, both the AC_VI backoff counter value and the AC_VO backoff counter value in the first link may be zero.

When backoff operations for two or more ACs in one link are successful, an internal collision resolution procedure may be performed to select one AC as a transmission target. In the internal conflict resolution procedure, an AC having a higher priority among two or more ACs may be selected. Since the priority of AC_VO is higher than that of AC_VI, AC_VO can be selected in the internal conflict resolution procedure. That is, it may be determined that the AC_VO backoff operation in the first link has succeeded. If the AC_VI backoff operation succeeds in the second link (eg, when the AC_VI backoff counter value is 0), the STA1 of STA MLD1 may transmit the AC_VO frame in the first link, and the STA2 of STA MLD1 may transmit the second AC_VI frames can be transmitted on the link. The AC_VO frame in the first link and the AC_VI frame in the second link may be simultaneously transmitted. The AC_VO frame may mean a data frame including a data unit for AC_VO (eg, an AC_VO physical layer protocol data unit (PPDU) or a medium access control (MAC) protocol data unit (MPDU)), and an AC_VI frame. may mean a data frame (eg, AC_VI PPDU or AC_VI MPDU) including a data unit for AC_VI.

The duration of the TXOP may be a time during which a communication node (eg, a TXOP holder) that obtains the TXOP maintains a medium without interference. A communication node may be an AP, STA, AP MLD, and/or STA MLD. The length of the TXOP may include the transmission time of the reception response frame, which is an immediate response transmitted to the TXOP holder. The reception response frame may be an acknowledgment (ACK) frame or a block ACK (BA) frame. The maximum length of TXOP (hereinafter referred to as “TXOP limit”) may be set for each AC. The AP may set an EDCA parameter set element including TXOP restriction information, and a management frame (eg, beacon frame, probe response frame) including the corresponding EDCA parameter set element , and / or an association response frame) may be transmitted to the STA. The default limit of TXOP for each AC may be set as shown in Table 3 below. The default limit of TXOP per AC may be set to a value different from Table 3.

STA1 can obtain a TXOP for transmission of the AC_VO frame on the first link, and STA2 can obtain a TXOP for transmission of the AC_VI frame on the second link. That is, STA1 may be a TXOP holder in the first link, and STA2 may be a TXOP holder in the second link. The TXOP obtained by STA1 in the first link may be set as the TXOP limit for the AC_VO frame. The TXOP obtained by STA2 on the second link may be set as the TXOP limit for the AC_VI frame. Simultaneous transmission operations may be initiated in the first link and the second link. The TXOP limit for AC_VO frames in the first link (hereinafter referred to as "AC_VO TXOP limit") may be shorter than the TXOP limit for AC_VI frames in the second link (hereinafter referred to as "AC_VI TXOP limit"). Accordingly, the STA MLD1 may not match the end time of the AC_VO frame transmitted on the first link with the end time of the AC_VI frame transmitted on the second link. That is, when padding is added to the AC_VO frame in the first link, since the AC_VO frame including the padding exceeds the AC_VO TXOP limit, to equalize the transmission end time of the AC_VI frame and the end time of the AC_VO frame in the first link Padding cannot be performed on the AC_VO frame.

Simultaneous transmission of the AC_VO frame in the first link and the AC_VI frame in the second link may be performed. In the first link, STA1 may adjust the length of an AC_VO frame (eg, AC_VO PPDU, AC_VO MPDU) in consideration of reception of a reception response frame (eg, BA (BlockAck) frame or Ack frame) and transmit the . Or, since STA2 is transmitting an AC_VI frame (eg, AC_VI PPDU, AC_VI MPDU) on the second link and the TXOP of STA2 (eg, the TXOP set to the AC_VI TXOP limit) is longer than the TXOP of STA1, STA1 receives a response Frames may not be received due to NSTR problems. Accordingly, STA1 may transmit the AC_VO frame using the entire acquired TXOP. STA1 may separately receive a reception response frame using methods to be described later. Since the STA2 of the STA MLD1 transmits the AC_VI frame within the AC_VI TXOP limit of the second link, the STA1 in the first link of the NSTR link pair relationship with the second link transmits the AC_VO frame for a time corresponding to the AC_VI TXOP limit of the second link. A reception response frame (eg, ACK frame, BA (block ACK) frame) cannot be received. That is, STA1 may not immediately receive a reception response frame for an AC_VO frame transmitted within the AC_VO TXOP limit of the first link. In this case, the reception response frame may be received based on at least one of three methods. Since the reception response frame for the AC_VO frame is not immediately received, the STA1 of the STA MLD1 transmits the ACK policy field included in the medium access control (MAC) header of the AC_VO frame to NSTR multi-link (ML) ACK. It can be set to an indicated value, and the corresponding AC_VO frame can be transmitted. AP1 may receive the AC_VO frame from STA1, and may confirm that the ACK policy field included in the MAC header of the AC_VO frame indicates NSTR ML ACK. In this case, AP1 may transmit the reception response frame for the AC_VO frame using at least one of the three methods. In an embodiment, an NSTR link pair may mean a link pair in which an STR operation of an STA MLD (eg, STA MLD1) cannot be performed. The STR link pair may refer to a link pair in which the STR operation of the STA MLD is performed.

- How to send and receive reception response frame 1-1

AP MLD1 may perform a backoff operation for transmission of an acknowledgment frame for the AC_VO frame in the first link where the data frame (eg, AC_VO frame) is received. If the value of the backoff counter for transmission of the reception response frame is 0, AP1 of AP MLD1 is able to receive the reception response frame after the point at which STA1 of STA MLD1 can receive it (eg, a data frame in the second link (eg, For example, after transmission of the AC_VI frame) is completed), a reception response frame for the AC_VO frame may be transmitted to the STA1. The interval from the end of the AC_VO frame in the first link (eg, completion of transmission) to the end of the AC_VI frame in the second link (eg, completion of transmission) may be a blindness section. STA1 may not be able to perform a reception operation in the blind section of the first link. Therefore, STA1 can perform a low-power operation in the blind section of the first link. For example, STA1 may operate in a micro sleep state in the blind section of the first link.

In the embodiment of FIG. 3, since STA1 and STA2 can perform simultaneous transmission operations and the AC_VO TXOP limit in the first link is shorter than the AC_VI TXOP limit in the second link, the STA1 determines the end time of the AC_VO frame and the AC_VI frame. It may not be possible to add padding to AC_VO frames to make them evenly matched. Therefore, STA1 of STA MLD1 may set the ACK policy field included in the MAC header of the AC_VO frame to a value indicating NSTR ML ACK, and may transmit the AC_VO frame. The ACK policy field set to a value indicating NSTR ML ACK may indicate transmission of the reception response frame for the AC_VO frame in the first link after completion of reception of the AC_VI frame in the second link. In this case, STA1 may not wait for reception of the reception response frame for the corresponding AC_VO frame after transmission of the AC_VO frame. Determination of whether the AC_VO frame is received may be delayed until after the reception response frame is received.

Instead of setting the ACK policy field included in the MAC header to a value indicating NSTR ML ACK, STA1 of STA MLD1 may transmit an AC_VO frame including an AC_VO data unit and a Block ACK Request (BAR). Alternatively, an AC_VO frame including the NSTR ML ACK indication of the ACK policy field included in the MAC header, the AC_VO data unit, and the BAR may be transmitted. That is, the AC_VO frame may have an aggregated-MAC protocol data unit (A-MPDU) form, and the BAR included in the AC_VO frame may indicate NSTR ML ACK. AP1 of AP MLD1 may receive the AC_VO frame on the first link and may check the value of the ACK policy field included in the AC_VO frame or whether the AC_VO frame includes BAR. If "the ACK policy field included in the AC_VO frame indicates NSTR ML ACK" and/or "if the AC_VO frame includes BAR (eg, BAR indicating NSTR ML ACK)", AP1 A backoff operation may be performed to transmit the reception response frame. A backoff operation for transmission of the reception response frame may be performed using an EDCA parameter of AC_VO (eg, a parameter for selecting an AC_VO backoff counter value).

When the backoff operation for transmitting the acknowledgment frame for the AC_VO frame is completed in the first link, AP1 transmits in the second link that has a relationship between the first link and an NSTR link pair (eg, AC_VI frame transmission operation) You can check if this is done. If the transmission operation is not completed in the second link, AP1 may perform a backoff operation for transmission of the reception response frame again. "When the backoff operation is completed in the first link and the transmission operation is completed in the second link, which is a relation between the first link and the NSTR link pair", AP1 of AP MLD1 transmits the reception response frame for the AC_VO frame in the first link. can STA1 of STA MLD1 may receive a reception response frame for the AC_VO frame from AP1.

Alternatively, if the backoff operation for transmitting the acknowledgment frame for the AC_VO frame in the first link succeeds once, AP1 of AP MLD1 waits until the transmission of the acknowledgment frame is possible, and then transmits the corresponding acknowledgment frame. there is. That is, the backoff counter value for the reception response frame may be maintained at 0 until reception of the AC_VI frame is completed in the second link. As another method, AP1 of AP MLD1 performs a backoff operation for transmitting the reception response frame from the point at which the reception response frame for the AC_VO frame can be transmitted (eg, the time when the reception of the AC_VI frame is completed in the second link). and may transmit a reception response frame when the backoff operation succeeds.

"The STA1 of the STA MLD1 does not immediately receive the reception response frame for the AC_VO frame" is "the ACK policy field included in the AC_VO frame transmitted on the first link", "the ACK policy field included in the AC_VO frame transmitted on the first link" BAR", and/or "BAR included in the form of an A-MPDU in an AC_VI frame transmitted by STA2 of STA MLD1 in a second link having a relationship between a first link and an NSTR link pair". BAR may indicate a time point at which STA1 of STA MLD1 receives the reception response frame. If the AC_VI frame received from STA2 of STA MLD1 includes BAR, AP MLD1 can check the time point at which the reception response frame can be received from STA1 based on the BAR, and at the checked time point, AC_VO frame through the first link A reception response frame for can be transmitted. That is, AP1 of AP MLD1 may transmit the reception response frame on the first link based on the above method 1-1.

The STA MLD1 may determine success or failure of transmission of the data frame in the first link based on the reception response frame received in the first link after completion of transmission of the data frame in the second link. After determining success or failure of data frame transmission, STA MLD1 may update EDCA parameters based on the determination result. If transmission of the data frame fails, STA MLD1 may double EDCA parameters for the first link. STA MLD1 may retransmit the failed data frame. If transmission of the data frame is successful, STA MLD1 may initialize EDCA parameters for the first link to initial values.

- How to send and receive reception response frame 1-2

The TXOP limit on the second link (eg AC_VI TXOP limit) may be longer than the TXOP limit on the first link (eg AC_VO TXOP limit). AP2 of AP MLD1 operating in the second link with the long TXOP limit set receives a reception response to a data frame (eg, AC_VI frame) received in the second link and a data frame (eg, AC_VI frame) received in the first link. AC_VO frame) may be transmitted together.

In the embodiment of FIG. 3, since STA1 and STA2 can perform simultaneous transmission operations and the AC_VO TXOP limit in the first link is shorter than the AC_VI TXOP limit in the second link, the STA1 determines the end time of the AC_VO frame and the AC_VI frame. It may not be possible to add padding to AC_VO frames to make them evenly matched. Therefore, STA1 of STA MLD1 may set the ACK policy field included in the MAC header of the AC_VO frame to a value indicating NSTR ML ACK, and may transmit the AC_VO frame. In this case, STA1 may not wait for reception of the reception response frame for the corresponding AC_VO frame after transmission of the AC_VO frame. Determination of whether the AC_VO frame is received may be delayed until after the reception response frame is received.

AP MLD1 (eg, AP1) may receive the AC_VO frame on the first link and may check the ACK policy field included in the MAC header of the AC_VO frame. When the ACK policy field indicates NSTR ML ACK, AP MLD1 may perform a procedure for transmitting a reception response frame for the AC_VO frame received on the first link on the second link. That is, the ACK policy field included in the AC_VO frame may indicate transmission of an acknowledgment frame for the AC_VO frame received on the first link through another link (eg, the second link). Alternatively, the above-described embodiment may be performed based on the BAR included in the AC_VO frame of the first link instead of the ACK policy field. Alternatively, the above-described embodiment may be performed based on the BAR included in the AC_VI frame of the second link instead of the ACK policy field. Alternatively, the embodiment may be performed in combinations of the methods described above. When the reception of the data frame (eg AC_VI frame) is completed in the second link having a relationship between the first link and the NSTR link pair, AP2 of AP MLD1 receives a reception response to the AC_VI frame received in the second link and the first link A reception response to the AC_VO frame received in may be transmitted through the second link. STA MLD1 (eg, STA2) may receive a reception response to the AC_VI frame and a reception response to the AC_VO frame through the second link.

A reception response to the AC_VI frame received on the second link and a reception response to the AC_VO frame received on the first link may be included in one reception response frame. In this case, the reception response frame may have an A-MPDU format. Alternatively, the reception response to the AC_VI frame received on the second link and the reception response to the AC_VO frame received on the first link may be included in different frames. That is, the reception response frame for the AC_VI frame received in the second link and the reception response frame for the AC_VO frame received in the first link may be transmitted through the second link.

"The STA1 of the STA MLD1 does not immediately receive an acknowledgment frame for the AC_VO frame" is the "ACK policy field" included in the AC_VO frame transmitted by the STA1 of the STA MLD1 in the first link, "STA MLD1 in the first link BAR included in the form of an A-MPDU in the AC_VO frame transmitted by the STA1 of the "," and/or "in the form of an A-MPDU in the AC_VI frame transmitted by the STA2 of the STA MLD1 in the second link in the relationship between the first link and the NSTR link pair Can be indicated by "included BAR". The BAR included in the AC_VI frame may request transmission of a reception response to the data frame (eg, AC_VO frame) received on the first link. That is, the BAR included in the AC_VI frame transmitted on the second link may request transmission of a reception response on the first link.

AP2 of AP MLD1 may receive an AC_VI data frame from STA2 of STA MLD1. When the AC_VI data frame includes BAR, AP2 of AP MLD1 may transmit a reception response frame for the data frame (eg, AC_VO frame) received in the first link through the second link. STA MLD1 may determine success or failure of transmission of the data frame in the first link based on the reception response frame received in the second link after completion of transmission of the data frame in the second link. After determining success or failure of data frame transmission, STA MLD1 may update EDCA parameters based on the determination result. If transmission of the data frame fails, STA MLD1 may double the EDCA parameters for the first link. STA MLD1 may retransmit the failed data frame. If transmission of the data frame is successful, STA MLD1 may initialize EDCA parameters for the first link.

- How to transmit/receive reception response frame 1-3

A reception response frame for a data frame (eg, AC_VO frame) transmitted in the first link may be transmitted in a third link that does not have a relationship between a first link and an NSTR link pair. In the embodiment of FIG. 3, since STA1 and STA2 can perform simultaneous transmission operations and the AC_VO TXOP limit in the first link is shorter than the AC_VI TXOP limit in the second link, the STA1 determines the end time of the AC_VO frame and the AC_VI frame. It may not be possible to add padding to AC_VO frames to make them evenly matched. Therefore, STA1 of STA MLD1 may set the ACK policy field included in the MAC header of the AC_VO frame to a value indicating NSTR ML ACK, and may transmit the AC_VO frame. In this case, STA1 may not wait for reception of the reception response frame for the corresponding AC_VO frame after transmission of the AC_VO frame. Determination of whether the AC_VO frame is received may be delayed until after the reception response frame is received.

AP MLD1 (eg, AP1) may receive the AC_VO frame on the first link and may check the ACK policy field included in the MAC header of the AC_VO frame. When the ACK policy field indicates NSTR ML ACK (eg, when the ACK policy field requests transmission of a reception response frame for the first link on a link other than the first link and NSTR link pair relationship) , AP MLD1 may perform a procedure for transmitting the reception response frame for the AC_VO frame received on the first link on a link other than the first link and NSTR link pair relationship (eg, third link) . AP MLD1 may select a link (eg, a third link) to transmit a reception response frame from among links mapped to the AC of the data frame received in the first link. Since the AC of the data frame received in the first link is AC_VO, AP MLD1 determines the relationship between the first link and the second link and the NSTR link pair among links mapped to AC_VO based on TID (traffic identifier)-to-link mapping. It is possible to select a link (eg, a third link) that is not. When TID-to-link mapping is set as default (eg, when all ACs are mapped to all links), AP MLD1 is not related to the first link and the second link among the links and the NSTR link pair. A link (eg, a third link) may be selected.

STA MLD1 may wait for reception of a reception response frame for a corresponding data frame in link(s) mapped to AC of a data frame including an ACK policy field indicating NSTR ML ACK. AP3 of AP MLD1 may perform a backoff operation in the third link to transmit a reception response frame for the data frame received in the first link. The backoff operation in the third link may be performed using parameters of AC_VO for the first link (eg, EDCA parameters). If the backoff operation succeeds in the third link, AP3 of AP MLD1 may check whether the reception response frame can be transmitted in the third link. That is, AP3 of AP MLD1 may check whether reception of the data frame has been completed in the first link and whether determination of the reception state of the corresponding data frame has been completed. If reception of the data frame is not completed in the first link, AP3 of AP MLD1 may repeatedly perform a backoff operation in the third link until the reception response frame is transmitted. Whenever a backoff operation is performed, the EDCA parameter may not be changed, and a new backoff counter value may be selected.

"When the third link can transmit the reception response frame and SIFS (short interframe space) has elapsed from the completion of data frame reception on the first link", AP3 of AP MLD1 performs a backoff operation on the third link A reception response frame may be transmitted at this successful time point. The start time of the backoff operation in the third link may be the start time of data frame transmission or the completion time of transmission of the data frame in the first link. Alternatively, the start time of the backoff operation in the third link may be the reception time of the BAR in the second link. STA MLD1 may determine success or failure of data frame transmission in the first link based on the reception response frame received in the third link. After determining success or failure of data frame transmission, STA MLD1 may update EDCA parameters based on the determination result. If transmission of the data frame fails, STA MLD1 may double the EDCA parameters for the first link. STA MLD1 may retransmit the data frame. If transmission of the data frame is successful, STA MLD1 may initialize EDCA parameters for the first link to initial values.

4 is a timing diagram illustrating a second embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.

Referring to FIG. 4, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA MLD1 may operate as an NSTR STA MLD in a specific link pair (eg, a pair of first and second links), and may operate as an NSTR STA MLD in another link pair (eg, a pair of first and third links and/or Alternatively, a pair of the second link and the third link) may operate as an STR STA MLD. That is, the STA MLD1 cannot perform the STR operation on the first link and the second link pair, and can perform the STR operation on the first link and the third link pair and/or the second link and the third link pair. can

AP MLD1 can transmit and receive data frames with STA MLD1 using multiple links. AP1 of AP MLD1 and STA1 of STA MLD1 may operate on a first link, AP2 of AP MLD1 and STA2 of STA MLD1 may operate on a second link, and AP3 of AP MLD1 and STA3 of STA MLD1 may operate on a third link. Links can work. Each of AP1 and STA1 may perform a backoff operation for frame transmission in a first link, each of AP2 and STA2 may perform a backoff operation for frame transmission in a second link, and each of AP3 and STA3 may perform a backoff operation for frame transmission in a second link. In link 3, a backoff operation for frame transmission can be performed.

The backoff operation may be performed independently on each of the links. The backoff operation may be an Enhanced Distributed Channel Access Function (EDCAF). A backoff operation on the links may be a backoff operation to the same AC. Alternatively, the backoff operation in the links may be a backoff operation for different ACs. Multiple backoff operations (eg, multiple backoff operations for multiple ACs) may be performed in one link. Value(s) of EDCA parameter(s) for backoff operation may be different for each AC.

In one of the first link and the second link (eg, the first link), the backoff operation may succeed first when the backoff counter value becomes 0. For example, in a link (eg, a first link) for which a small backoff counter value is selected, the backoff operation may succeed first. When a plurality of backoff operations for a plurality of ACs are simultaneously performed, a backoff operation in which a backoff counter value first reaches 0 may be determined to be successful. If the backoff operation succeeds, a data frame for an AC (eg, AC_BE) that is the target of the backoff operation may be transmitted at a boundary of a slot in which a backoff counter value becomes 0.

If the AC_BE backoff operation succeeds in the first link, AP1 of AP MLD1 may transmit a data frame (eg, AC_BE frame) in the first link. The TXOP obtained by AP1 in the first link may be set as a TXOP limit for the AC_BE frame. The AC_VI backoff operation in the second link may succeed while the frame of data is being transmitted in the first link. In this case, AP2 of AP MLD1 may transmit a data frame for an AC (eg, AC_VI), which is a target of a backoff operation, at a boundary of a slot in which a backoff counter value becomes 0. In the first link and the second link, data frames may be transmitted to the same STA MLD (eg, STA MLD1). STA MLD1 receiving the data frame may be an NSTR STA MLD in a specific link pair (eg, a first link pair and a second link pair).

The AC_VI TXOP limit for the AC_VI frame in the second link may be shorter than the AC_BE TXOP limit for the AC_BE frame in the first link. Accordingly, AP MLD1 may not match the end time of the AC_VI frame transmitted on the second link with the end time of the AC_BE frame transmitted on the first link. That is, when padding is added to the AC_VI frame in the second link, since the AC_VI frame including the padding exceeds the AC_VI TXOP limit, to match the transmission end time of the AC_BE frame and the end time of the AC_VI frame in the second link Padding cannot be performed on the AC_VI frame.

AP MLD1 may check the following condition(s) to set the ACK policy field (eg, ACK policy indicator) in the MAC header of the data frame to be transmitted on the second link.

-Condition 1: A data frame is being transmitted on a link different from the second link (eg, the first link), and the receiver of the data frame being transmitted on the first link and the receiver of the data frame to be transmitted on the second link are the same NSTR STA If MLD

-Condition 2: When transmission of a data frame in the second link is terminated while transmission of the data frame in the first link

-Condition 3: When the TXOP limit of the AC of the data frame to be transmitted in the second link is shorter than the remaining length of the TXOP set in the first link

If the above condition(s) is satisfied, STA2 of STA MLD1 transmits a frame (e.g., AC_VI Receive response frame for the frame) cannot be transmitted. Therefore, so that STA2 of STA MLD1 does not immediately transmit the reception response frame for the data frame, AP2 of AP MLD1 sets the ACK policy field included in the MAC header of the data frame (eg, AC_VI frame) to ML ACK (eg, AC_VI frame). , NSTR ML ACK), and the corresponding data frame can be transmitted in the second link. The ACK policy field indicating ML ACK may indicate transmission of a reception response frame for a data frame in another method.

- How to transmit/receive reception response frame 2-1

AP2 of AP MLD1 may set the ACK policy field included in the MAC header of the data frame (eg, AC_VI frame) to a value indicating ML ACK (eg, NSTR ML ACK), and 2 links can transmit. In this case, AP MLD1 may suspend the determination of success or failure of transmission of the data frame, and may check the reception response frame for the data frame (eg, AC_BE frame) transmitted in the first link.

STA MLD1 may receive a data frame (eg, AC_VI frame) on the second link, and confirm that the ACK policy field included in the MAC header of the corresponding data frame indicates ML ACK. In this case, the STA MLD1 may determine to transmit the reception response frame for the data frame received in the second link through the first link based on the information indicated by the ACK policy field. Alternatively, the above-described embodiment may be performed based on the BAR included in the AC_VI frame of the second link instead of the ACK policy field. Alternatively, the above-described embodiment may be performed based on the BAR included in the AC_BE frame of the first link instead of the ACK policy field. Alternatively, the embodiment may be performed in combinations of the methods described above. The STA MLD1 may transmit a reception response to the data frame received on the first link and a reception response to the data frame received on the second link through the first link. The reception response frame for the data frame received in the first link may include reception response information for the data frame received in the second link.

AP1 of AP MLD1 may transmit a data frame on the first link and may receive a reception response frame from STA1 of STA MLD1 on the first link. The reception response frame received in the first link may include a reception response to the data frame transmitted in the first link and a reception response to the data frame transmitted in the second link. AP MLD1 may determine success or failure of transmission of the data frame in the second link based on the reception response frame received in the first link. After determining the success or failure of transmission of the data frame, AP MLD1 may update the EDCA parameters for the second link based on the determination result. If transmission of the data frame fails, AP MLD1 may double the EDCA parameters for the second link. AP MLD1 may retransmit the failed data frame. If transmission of the data frame is successful, AP MLD1 may initialize EDCA parameters for the second link to initial values.

A data frame transmitted on the first link may include a BAR. The BAR may include an indicator requesting transmission of a reception response frame for a data frame transmitted on the second link through the first link. STA1 of STA MLD1 may receive the data frame through the first link and may check the BAR included in the data frame. STA1 of STA MLD1 may confirm that transmission of a reception response frame for a data frame transmitted on the second link through the first link is requested based on the BAR. Accordingly, the STA1 of the STA MLD1 may transmit a reception response to the data frame received through the first link and a reception response to the data frame received by the STA2 of the STA MLD1 through the second link through the first link. Method 2-1 in the embodiment of FIG. 4 may be a method corresponding to method 1-2 in the embodiment of FIG. 3 described above.

- How to transmit/receive reception response frame 2-2

The STA2 of the STA MLD1 may repeatedly perform a backoff operation for transmission of the corresponding reception response frame after receiving the data frame in the second link until the point at which the reception response frame for the corresponding data frame can be transmitted. If the backoff operation for transmission of the corresponding reception response frame succeeds after the time at which the reception response frame can be transmitted (for example, the time when the reception of the AC_BE frame is completed in the first link), the STA2 of the STA MLD1 in the second link A reception response frame may be transmitted. Method 2-2 in the embodiment of FIG. 4 may be a method corresponding to method 1-1 in the embodiment of FIG. 3 described above.

- How to send and receive reception response frame 2-3

AP2 of AP MLD1 may set the ACK policy field included in the MAC header of the data frame (eg, AC_VI frame) to a value indicating ML ACK (eg, NSTR ML ACK), and 2 links can transmit. STA2 of STA MLD1 may receive the data frame on the second link, and may confirm that the ACK policy field included in the MAC header of the data frame indicates ML ACK. In this case, the STA MLD1 transmits a reception response frame for a data frame received through the second link in a link (eg, a third link) other than the relationship between the first link and the second link and the NSTR link pair A backoff operation may be performed for STA MLD1 may select a link (eg, a third link) to transmit a reception response frame from among links mapped to the AC of the data frame received on the second link. Since the AC of the data frame received in the second link is AC_VI, the STA MLD1 selects links that are not in a relationship between the first link and the second link and the NSTR link pair among the links mapped to AC_VI based on the TID-to-link mapping ( For example, a third link) may be selected. The STA3 of the STA MLD1 may transmit a reception response frame for the data frame received on the first link through the third link. A backoff operation may be performed to transmit the reception response frame in the third link.

The backoff operation performed by the STA3 of the STA MLD1 in the third link may be repeatedly performed until a reception response frame for the data frame received through the second link is transmitted. When "reception of the data frame is completed in the second link and confirmation of the reception state of the corresponding data frame is completed", a reception response frame may be generated. The backoff operation may be repeatedly performed from at least the reception start time of the data frame to the end time of the corresponding data frame until the SIFS elapses. The backoff operation in the third link may be performed using AC_VI parameters (eg, EDCA parameters) for the second link. Alternatively, the backoff operation in the third link may use the AC_VO parameter for fast transmission of the reception response frame. Whenever a backoff operation is performed, the EDCA parameter may not be changed, and a new backoff counter value may be selected. If the backoff operation succeeds in the third link, the STA3 of the STA MLD1 may check whether the reception response frame can be transmitted in the third link. That is, the STA3 of the STA MLD1 may check whether the reception of the data frame has been completed in the second link and whether the determination of the reception state of the corresponding data frame has been completed. "If the third link can transmit a reception response frame, and SIFS has elapsed from the completion of data frame reception on the second link", STA3 of STA MLD1 receives when the backoff operation succeeds in the third link A response frame may be transmitted. Method 2-3 in the embodiment of FIG. 4 may be a method corresponding to method 1-3 in the embodiment of FIG. 3 described above.

5 is a timing diagram illustrating a third embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.

Referring to FIG. 5, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA MLD1 may simultaneously transmit data frames on the first link and the second link. An AC of a data frame transmitted on the first link may be different from an AC of a data frame transmitted on the second link. For example, the AC_VO frame in the first link and the AC_VI frame in the second link may be simultaneously transmitted. The AC_VO TXOP limit may be shorter than the AC_VI TXOP limit. When the NSTR MLD performs simultaneous transmission using multiple links, the data frame may be configured according to the short TXOP limit (eg, AC_VO TXOP).

A fragmentation operation on a data unit (eg, AC_VI frame) transmitted in the AC_VI TXOP limit of the second link may be performed according to the AC_VO TXOP limit in the first link. When a data frame transmitted in the second link is generated in the form of an A-MPDU, the corresponding A-MPDU may be configured according to the AC_VO TXOP length in the first link. In the A-MPDU construction procedure, padding may be added to the data frame (eg A-MPDU) of the second link in order to conform to the AC_VO TXOP limit in the first link.

STA MLD1 may configure the AC_VO frame to transmit the AC_VO frame within the AC_VO TXOP limit on the first link and receive the reception response frame (eg, BA frame) for the AC_VO frame, and transmit the AC_VO frame can transmit STA MLD1 transmits the AC_VI frame on the second link at the same time as the AC_VO frame of the first link and configures the AC_VI frame to receive a reception response frame (eg, BA frame) for the corresponding AC_VI frame, , the corresponding AC_VI frame can be transmitted. After synchronous transmission of data frames in the first link and the second link, the STA MLD1 may transmit the remaining AC_VI frames after performing a backoff operation again in the second link. Alternatively, if the remaining length of the AC_VI frame in the second link can be transmitted within the remaining TXOP, the STA2 of STA MLD1 may not perform the backoff operation again, and may transmit the remaining frames after SIFS from the BA frame reception time .

6 is a timing diagram illustrating a fourth embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.

Referring to FIG. 6, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA MLD1 may simultaneously transmit data frames on the first link and the second link. An AC of a data frame transmitted on the first link may be different from an AC of a data frame transmitted on the second link. For example, the AC_VO frame in the first link and the AC_VI frame in the second link may be simultaneously transmitted. The AC_VO TXOP limit may be shorter than the AC_VI TXOP limit. When the NSTR MLD performs simultaneous transmission using multiple links, the data frame may be configured according to the short TXOP limit.

The AC_VO TXOP limit on the first link may be extended according to the length of the data frame transmitted on the second link. That is, it may be allowed that the transmission of the data frame ends after the TXOP limit. STA MLD1 (e.g., STA1) may transmit a data frame (e.g., AC_VO frame) within the extended TXOP limit, and transmit a data unit present in the queue in the remaining time within the extended TXOP limit It can perform an operation or a transmission operation of padding. The STA1 of the STA MLD1 may select to transmit a data unit (eg, AC_VI data unit) for which the backoff operation succeeded but was not selected by the internal collision resolution procedure among data units existing in the queue. Alternatively, STA1 of STA MLD1 may transmit a data frame or data unit of an AC having the same priority as or a higher priority than the AC of a data frame transmitted in the extended TXOP limit.

7 is a timing diagram illustrating a fifth embodiment of a method of transmitting and receiving frames when TXOP restrictions are different from each other in a WLAN system supporting multiple links.

Referring to FIG. 7, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. An AC (eg, AC_VO) of a data frame transmitted on the first link may be different from an AC (eg, AC_VI) of a data frame transmitted on the second link. The AC_VO TXOP limit may be shorter than the AC_VI TXOP limit. When the NSTR MLD performs simultaneous transmission using a plurality of links, transmission of data frames may be delayed within the short TXOP limit so that data frames transmitted on the links have the same end time.

In order to match the end time of the AC_VO frame in the first link and the end time of the AC_VI frame in the second link, transmission of the AC_VO frame in the first link may be delayed. If the time from the start of transmission of the AC_VI frame in the second link to the start of transmission of the delayed AC_VO frame in the first link is longer than the time required for transmission of the QoS Null frame or clear to send (CTS)-to-Self frame, STA MLD1 may transmit a QoS Null frame or a CTS-to-Self frame including a duration field set equal to the value of the duration field of the AC_VI frame transmitted on the second link to the first link. The QoS Null frame (or CTS-to-Self frame) in the first link and the AC_VI frame in the second link can be simultaneously transmitted. In the first link, the QoS Null frame (or CTS-to-Self frame) may be transmitted based on the parameter (eg, TXOP limit) for the AC_VI frame in the second link.

8 is a timing diagram illustrating a sixth embodiment of a method for transmitting and receiving frames when TXOP restrictions are different from each other in a wireless LAN system supporting multiple links.

Referring to FIG. 8 , AP MLD1 may transmit and receive data frames with STA MLD1 using multiple links. AP1 of AP MLD1 and STA1 of STA MLD1 may operate on a first link, and AP2 of AP MLD1 and STA2 of STA MLD1 may operate on a second link. Each of AP1 and STA1 may perform a backoff operation for frame transmission in the first link, and each of AP2 and STA2 may perform a backoff operation for frame transmission in the second link.

The backoff operation may be performed independently on each of the links. The backoff operation may be an Enhanced Distributed Channel Access Function (EDCAF). A backoff operation on the links may be a backoff operation to the same AC. Alternatively, the backoff operation in the links may be a backoff operation for different ACs. Multiple backoff operations (eg, multiple backoff operations for multiple ACs) may be performed in one link. Value(s) of EDCA parameter(s) for backoff operation may be different for each AC.

The backoff operation for synchronous transmission may be performed for the same AC in both the first link and the second link, and may use the same EDCA parameter(s). Counter values for backoff operations in the first link and the second link may be independently selected. The counter value may mean a backoff counter value. In one of the first link and the second link (eg, the first link), the backoff operation may succeed first when the backoff counter value becomes 0. For example, in a link (eg, a first link) for which a small backoff counter value is selected, the backoff operation may succeed first. In the first link where the backoff operation succeeds, the value of the backoff counter may be maintained at 0 until the AC_VI backoff operation succeeds in another link (eg, the second link). In this case, transmission in the first link may be delayed (ie, standby).

STA1 of STA MLD1 simultaneously performs a backoff operation for AC_VI (hereinafter referred to as "AC_VI backoff operation") and a backoff operation for AC_VO (hereinafter referred to as "AC_VO backoff operation") in the first link. can The AC_VI backoff operation may succeed before the AC_VO backoff operation, and the AC_VI backoff counter value in the first link may be maintained at 0 until the backoff counter value in the second link becomes 0. The AC_VO backoff operation may be completed while waiting for transmission of AC_VI data in the first link. In this case, both the AC_VI backoff counter value and the AC_VO backoff counter value in the first link may be zero.

When backoff operations for two or more ACs in one link are successful, an internal collision resolution procedure may be performed to select one AC as a transmission target. In the internal conflict resolution procedure, a backoff operation for an AC such as an AC in backoff operation on another link may be selected. Since the AC_VI backoff operation is in progress in the second link, the AC_VI backoff operation in the first link can be selected. That is, it may be determined that the AC_VI backoff operation in the first link has succeeded. Alternatively, when AC_VO backoff is in progress also in the second link, an AC_VO backoff operation having a higher priority than AC_VI may be selected in the first link according to the priorities in Table 1.

If the AC_VI backoff operation succeeds in the second link (eg, when the AC_VI backoff counter value is 0), the STA1 of the STA MLD1 may transmit the AC_VI frame in the first link, and the STA2 of the STA MLD1 may transmit the second AC_VI frames can be transmitted on the link. TXOP on each link can be set to AC_VI TXOP limit. The AC_VI frame in the first link and the AC_VI frame in the second link may be simultaneously transmitted. The TXOP limit for each AC in the first link and the second link may be the same. Accordingly, transmission end points may be synchronized through padding or the like. The above-described embodiment can also be applied when downlink transmission is performed from the AP MLD to the STA MLD.

9A is a timing diagram illustrating a first embodiment of a multi-user (MU) transmission method in a WLAN system supporting multiple links, and FIG. 9B is a timing diagram illustrating a second embodiment of a MU transmission method in a WLAN system supporting multiple links. It is a timing diagram illustrating an embodiment.

Referring to FIGS. 9A and 9B , the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). can be referred to. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA MLD1 may participate in Orthogonal Frequency Division Multiple Access (OFDMA) MU transmission in multiple links. STA1-1 of STA MLD1 may participate in downlink OFDMA MU transmission on the first link, receive a data frame through a subchannel on the first link, and transmit a reception response frame for the data frame through a subchannel. can While AP1 of AP MLD1 performs downlink OFDMA MU transmission on the first link, AP2 of AP MLD1 may transmit a trigger frame (TF) for uplink OFDMA MU transmission on the second link. The STA MLD1 may receive a TF from the AP MLD1, and the STA(s) associated with the STA MLD1 transmit a data frame (eg, Trigger Based (TB) PPDU) through a subchannel after SIFS from the time of receiving the TF to the AP2 can be sent to Even when STA MLD1, which is an NSTR STA MLD, receives a TF triggering uplink transmission, it may not be able to perform uplink transmission if a downlink OFDMA MU reception operation is being performed. Accordingly, AP MLD1 may not transmit a TF including uplink resource allocation information for STA1-1 of STA MLD1 performing a reception operation on the first link and STA 1-2 of link 2, which is an NSTR link pair. That is, the TF for which AP MLD1 triggers uplink OFDMA MU transmission on the second link may not include uplink resource allocation information for STA1-2.

In the embodiment of FIG. 9B, STA1-1 of STA MLD1, which is an NSTR STA MLD, transmits a data frame (eg, TB PPDU) in a subchannel indicated by a TF triggering uplink OFDMA MU transmission on the first link. and receive a reception response frame for the data frame. While STA1-1 of STA MLD1 is performing uplink OFDMA MU transmission on the first link, STA1-2 of STA MLD1 may not receive a TF triggering uplink OFDMA MU transmission from AP2 of AP MLD1 on the second link. there is. Accordingly, AP MLD1 (eg, AP2) may not transmit a TF including uplink resource allocation information for STA MLD1 performing a reception operation on the first link. That is, the TF for which AP MLD 1 triggers uplink OFDMA MU transmission on the second link may not include uplink resource allocation information for STA1-2.

10 is a timing diagram illustrating a third embodiment of an MU transmission method in a WLAN system supporting multiple links.

Referring to FIG. 10, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. STA1-1 of STA MLD1 may participate in downlink OFDMA MU transmission on the first link, receive a data frame through a subchannel on the first link, and transmit a reception response frame for the data frame through a subchannel. can While AP1 of AP MLD1 performs downlink OFDMA MU transmission on the first link, AP2 of AP MLD1 may transmit a TF for uplink OFDMA MU transmission on the second link.

STA MLD1 may receive a TF including uplink resource allocation information on a second link while receiving a downlink OFDMA MU on a first link. In this case, the STA MLD1 cannot perform the channel sensing operation for a preset time (eg, SIFS) in the second link, and transmits using uplink resources indicated by the TF without performing the channel sensing operation. can be done Alternatively, STA 1-2 of STA MLD1 may perform a channel sensing operation on the second link for a preset time and then perform an uplink transmission operation on the second link. However, the above-described uplink transmission operation of STA MLD1 in the second link may interfere with the first link. Accordingly, STA MLD1 may not be able to perform the above-described uplink transmission operation in the second link. AP2 of AP MLD1 sets the TF transmission end time in the second link and the downlink transmission end time in the first link for a certain period of time after completion of the backoff operation in the second link (for example, in the first link). The TF may be transmitted after waiting for a time during which the downlink transmission end point and the end point of the second link TF are the same. Through the above-described operation of waiting for AP2 of AP MLD1 to transmit TF on the second link, uplink transmission of STA1-2 of the second link does not affect downlink data reception of STA1-1 of the first link. may not be

11 is a timing diagram illustrating a fourth embodiment of a MU transmission method in a WLAN system supporting multiple links.

Referring to FIG. 11, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. AP1 and AP2 of AP MLD1 may perform a backoff operation for TF transmission to perform uplink OFDMA MU transmission on the first link and the second link. STA MLD1, which is an NSTR STA MLD, may not be able to transmit a frame in another link while receiving a frame in one link. In order for STA MLD1 to participate in uplink OFDMA MU transmission in the first link and the second link, the transmission period of the TF and the uplink data frame must be synchronized. That is, synchronous transmission of TFs must be performed in the first link and the second link, and the TF transmission completion time must be the same. Even if the backoff operation for TF transmission in the first link succeeds before the backoff operation for TF transmission in the second link, AP MLD1 continues to perform the first operation until the backoff operation for TF transmission in the second link is completed. Can wait for TF transmission on the link. That is, AP MLD1 can simultaneously transmit TFs on the first link and the second link.

The length of the TF transmitted on the first link and the length of the TF transmitted on the second link may vary depending on the number of STAs whose transmission is triggered by the corresponding TF. A short-length TF may be set to match a long-length TF. When TFs use different modulation and coding schemes (MCSs), a TF with a short transmission time may be set according to a TF with a long transmission time. The above-described operation may be performed regardless of the number of STAs for which transmission is triggered by the TF. According to the above-described operation, the transmission completion time of TFs in multiple links can be set identically. In order to equalize transmission times of TFs in multiple links, a padding operation for TFs may be performed.

STA MLD1 may receive a TF from AP MLD1 and perform uplink transmission using resources allocated by the TF. STA MLD1, which is an NSTR STA MLD, may not receive a frame on another link while performing uplink transmission on one link. Accordingly, AP MLD1 may allocate uplink resources such that uplink resources allocated by TFs in multiple links are terminated at the same time point. STAs of STA MLD1 may transmit frames according to uplink resources allocated by TF. And, STA(s) of other STA MLD(s) triggered by AP MLD 1 may transmit frames according to uplink resources allocated by TF. To support the above-described operation, the STA(s) of STA MLD1 may add padding to the data frame. And, STA(s) of other STA MLD(s) triggered by AP MLD 1 may add padding to the data frame.

12 is a timing diagram illustrating a fifth embodiment of an MU transmission method in a WLAN system supporting multiple links.

Referring to FIG. 12, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. When uplink OFDMA MU transmission is performed multiple times, if STA MLD1, which is an NSTR STA MLD, participates in uplink OFDMA MU transmission, the transmission period and the reception period must be synchronized. Since STA MLD1 participates in uplink OFDMA MU transmission, synchronization transmission for TF in the first link and TF in the second link can be performed, and the transmission completion time of TF in the first link and TF in the second link The transmission completion point may be synchronized. The lengths of uplink data frames transmitted on subchannels in the first link and the second link may be set to be the same, and the STA (s) of the STA MLD (s) triggered by the TF of AP MLD1 transmits the uplink data You can add padding to . Accordingly, end points of uplink transmission in the first link and the second link may be synchronized.

The reception response frame (eg, BA frame) transmitted by AP MLD1 may include a TF for transmission of the next uplink OFDMA MU. A BA frame including the above TF may be referred to as "BA frame + TF". For example, BA frame + TF may be configured in the form of an A-MPDU. Alternatively, the BA frame + TF may be configured as a separate frame and subsequently transmitted. The length of the BA frame and the length of the TF may vary depending on the number of STAs participating in uplink OFDMA MU transmission and/or MCS. Accordingly, when STA MLD1, which is an NSTR STA MLD, participates in uplink OFDMA MU transmission in the first link and the second link, AP MLD1 may perform synchronization transmission for "BA frame + TF". The transmission start time and transmission end time of "BA frame + TF" in the first link may be the same as the transmission start time and transmission end time of "BA frame + TF" in the second link. In order to synchronize transmission end points of the BA frame + TF in the first link and the second link, padding may be added to the BA frame + TF in the second link. AP MLD1 may allocate uplink resources so that uplink transmission intervals in the first link and the second link are synchronized. When the transmission of the NSTR STA MLD is not performed after the transmission of the BA frame (eg, when AP MLD 1 no longer allocates uplink resources), the transmission end point of the BA frame in the first link and the second link may not be synchronized.

13 is a timing diagram illustrating a sixth embodiment of a MU transmission method in a WLAN system supporting multiple links.

Referring to FIG. 13, the AP MLD supporting the STR operation may be referred to as STR AP MLD, and the non-AP MLD not supporting the STR operation may be referred to as NSTR non-AP MLD (or NSTR STA MLD). there is. AP MLD1 may be STR AP MLD, and STA MLD1 may be NSTR STA MLD. AP MLD1 may perform downlink OFDMA MU transmission on the second link while performing downlink OFDMA MU transmission on the first link. STA MLD1 (eg, STA1-1 and STA1-2), which are NSTR STA MLDs, may participate in downlink OFDMA MU transmission on the first link and the second link. Transmission end times of downlink data transmitted on the first link and the second link may be different due to a difference in backoff end times between the first link and the second link or a difference in MCS of downlink data. Since STA MLD1 cannot perform the STR operation, downlink OFDMA MU transmission in the first link and the second link must end at the same time. To support this operation, padding may be added to the downlink frame. The length of the padding may be the same as the transmission end point of the downlink data transmitted on the second link and the first link.

When uplink OFDMA MU transmission is performed after downlink OFDMA MU transmission, a specific frame in the downlink OFDMA MU transmission procedure may include a TF for uplink OFDMA MU transmission. When the NSTR STA MLD participates in downlink and/or uplink OFDMA MU transmission, synchronization transmission may be required. In this case, the uplink OFDMA transmission period allocated by the TF in multiple links may be the same time period in the first link and the second link. STA(s) may perform uplink transmission (eg, transmission of an uplink data frame) in the time interval allocated by the TF, and may transmit padding in the remaining time interval. If transmission of the NSTR STA MLD is not performed after transmission of the BA frame, transmission end points of the BA frame in the first link and the second link may not be synchronized.

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims below. You will be able to.

Claims (20)

As a method of the first device,
receiving a first frame from a second device at a first transmit opportunity (TXOP) of a first link;
receiving a second frame from the second device in a second TXOP of a second link;
performing a first backoff operation for transmission of a first reception response frame for the first frame in the first link; and
Transmitting the first reception response frame from the first link to the second device when "the first backoff operation is completed and reception of the second frame is completed";
The first TXOP is shorter than the second TXOP, and the reception completion time of the second frame is after the reception completion time of the first frame, the method of the first device. The method of claim 1,
An acknowledgment (ACK) policy field included in a medium access control (MAC) header of the first frame is set to a value indicating a non-simultaneous transmit and receive (NSTR) multi-link (ML) ACK, and the NSTR ML ACK The ACK policy field set to a value indicating instructs to transmit the first reception response frame after completion of reception of the second frame, the method of the first device. The method of claim 1,
The first frame includes a block ACK request (BAR) indicating NSTR ML ACK, and the BAR instructs to transmit the first reception response frame after completion of reception of the second frame. Method of the first device . The method of claim 1,
The first backoff operation is performed using an enhanced distributed channel access (EDCA) parameter for an access category (AC) of the first frame. The method of claim 1,
The first back-off operation is repeatedly performed until reception of the second frame is completed, or when the first back-off operation is completed before reception of the second frame is completed, the back-off operation for the first back-off operation is completed. The counter value is maintained at 0 until reception of the second frame is completed, or the first backoff operation is performed after reception of the second frame is completed. The method of claim 1,
When the first device is an access point (AP) multi-link device (MLD), the second device is a station (STA) MLD, and when the first device is the STA MLD, the second device is the AP MLD, the AP MLD supports a simultaneous transmit and receive (STR) operation in the first link and the second link, and the STA MLD does not support the STR operation in the first link and the second link , the method of the first device. The method of claim 6,
STA (station) 1 associated with the STA MLD performs a low-power operation in a period from the end of the first frame to the end of the second frame in the first link. Method of the first device. As a method of the first device,
receiving a first frame from a second device at a first transmit opportunity (TXOP) of a first link;
receiving a second frame from the second device in a second TXOP of a second link; and
When the information included in the first frame indicates that the first reception response to the first link is to be transmitted through the second link, the first reception response to the first frame and the second frame Transmitting a second reception response to the second link to the second device,
The first TXOP is shorter than the second TXOP, and the reception completion time of the second frame is after the reception completion time of the first frame, the method of the first device. The method of claim 8,
The information is an acknowledgment (ACK) policy field included in a medium access control (MAC) header of the first frame, and the ACK policy field is set to a value indicating NSTR ML ACK. The method of claim 8,
The information is a block ACK request (BAR) included in the first frame, the method of the first device. The method of claim 8,
The step of transmitting to the second device,
generating one reception response frame including the first reception response and the second reception response; and
And transmitting the one reception response frame to the second device. The method of claim 8,
The step of transmitting to the second device,
Transmitting a first reception response frame including the first reception response to the second device; and
And transmitting a second reception response frame including the second reception response to the second device. The method of claim 8,
When the first device is an access point (AP) multi-link device (MLD), the second device is a station (STA) MLD, and when the first device is the STA MLD, the second device is the AP MLD, the AP MLD supports a simultaneous transmit and receive (STR) operation in the first link and the second link, and the STA MLD does not support the STR operation in the first link and the second link , the method of the first device. As a method of the first device,
receiving a first frame from a second device at a first transmit opportunity (TXOP) of a first link;
receiving a second frame from the second device in a second TXOP of a second link; and
Requesting that the information included in the first frame transmits a first reception response frame for the first frame on a third link that is not in a relationship between the first link and a non-simultaneous transmit and receive (NSTR) link pair case, transmitting the first reception response frame to the second device on the third link. The method of claim 14,
The first link and the second link are the NSTR link pair, the first TXOP is shorter than the second TXOP, and the reception completion time of the second frame is after the reception completion time of the first frame. device method. The method of claim 14,
The step of transmitting to the second device,
selecting the third link having no relationship between the first link and the NSTR link pair among links mapped to an access category (AC) of the first frame;
performing a first backoff operation for transmission of the first reception response frame in the third link; and
and transmitting the first reception response frame to the second device through the third link when the first backoff operation is completed. The method of claim 16
The method of claim 1 , wherein the third link is selected based on a traffic identifier (TID)-to-link mapping. The method of claim 16
wherein the first backoff operation in the third link is performed using an enhanced distributed channel access (EDCA) parameter for the AC of the first frame. The method of claim 14,
The information is an acknowledgment (ACK) policy field included in a medium access control (MAC) header of the first frame, and the ACK policy field is set to a value indicating NSTR multi-link (ML) ACK. First device way of. The method of claim 14,
When the first device is an access point (AP) multi-link device (MLD), the second device is a station (STA) MLD, and when the first device is the STA MLD, the second device is the AP MLD, the AP MLD supports the STR operation in the first link and the second link, and the STA MLD does not support the STR operation in the first link and the second link, the method of the first device .

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